Multilayer dielectric tunnel barrier used in magnetic tunnel junction devices, and its method of fabrication

ABSTRACT

A multilayer dielectric tunnel barrier structure and a method for its formation which may be used in non-volatile magnetic memory elements comprises an ALD deposited first nitride junction layer formed from one or more nitride monolayers i.e., AlN, an ALD deposited intermediate oxide junction layer formed from one or more oxide monolayers i.e., Al x O y , disposed on the first nitride junction layer, and an ALD deposited second nitride junction layer formed from one or more nitride monolayers i.e., AlN, disposed on top of the intermediate oxide junction layer. The multilayer tunnel barrier structure is formed by using atomic layer deposition techniques to provide improved tunneling characteristics while also providing anatomically smooth barrier interfaces.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates generally to the field of semiconductormemory, sensor applications and logic devices. The invention relatesmore specifically to a multilayer dielectric tunnel barrier used inmagnetic tunnel junction devices, and its method of fabrication.

[0003] 2. Description of the Related Art

[0004] Recently, magnetoresistive random access memory (MRAM) deviceshave been developed as possible use for data storage. The nonvolatility,fast access times, and less complex structure of MRAM offers someadvantages over DRAM and FLASH memory devices.

[0005] The two most critical layers in an MRAM memory cell are thetunnel barrier, which is often formed with Al_(x)O_(y) i.e., Al₂O₃, andthe sense (free) layer. The tunnel barrier is very thin and thetunneling resistance is exponentially dependent on its thickness. Thisstrong dependence on thickness makes it difficult to consistentlyproduce devices with nearly the same resistance over typical substratesizes currently used in memory manufacturing processes.

[0006] A magnetic tunnel junction device, in its simplest form, is twoferromagnetic layers separated by the tunnel barrier or dielectric film.The two ferromagnetic layers, together with the tunnel barrier, act topass certain electrons preferentially based on their respective spins.One ferromagnetic layer has a pinned magnetic field whereas the otherferromagnetic layer has a magnetic field which freely switchesdirections based on the applied magnetic programming signal.

[0007] For proper device operation, the tunnel barrier must be free ofpinholes, very smooth, and uniform over the entire wafer. Smallvariations in the thickness of the tunnel barrier layer such as over thesurface of a wafer, can result in large variations in memory cellresistance. Typically, an Al_(x)O_(y) tunnel barrier layer is fabricatedby depositing a metallic aluminum layer and subsequently oxiding thislayer by one of several methods. Oxidation can occur by plasmaoxidation, oxidation in air, oxidation by glow-discharge plasma,atomic-oxygen exposure, and ultraviolet-stimulated oxygen exposure.

[0008] However, the oxidation process creates anomalous effects.Overoxidation or underoxidation occurring on the aluminum layer reducesthe magnetoresistance ratio. The magnetoresistance ratio is typicallythe change of resistance proportional to the square of the magneticfield. Overoxidation results in oxidation of the magnetic electrodebeneath the tunnel barrier; whereas, underoxidation leaves metallicaluminum at the bottom of the tunnel barrier. In addition, roughness atthe tunnel barrier interfaces lowers the magnetoresistance ratiodramatically, due to partial shorts or tunneling hot spots. Thus,producing a magnetic tunnel junction material with good resistanceuniformity over an entire wafer is challenging. Many techniques havebeen employed to improve the aluminum metal layer thickness uniformity,such as forming the Al_(x)O_(y) tunnel barrier with air, reactivesputtering, plasma oxidation with plasma source, plasma oxidation withpower introduced from the target side, and plasma oxidation with powerintroduced from the substrate side.

[0009] Another problem arises when the magnetic tunnel junction materialis exposed to temperatures greater than 300° C. The magnetoresistanceratio begins to degrade at 300° C. and drops off sharply at 400° C. as aresult of increasing resistance. In addition, as bit sizes are reduced,a challenge arises in producing magnetic tunnel junction material withvery low resistance-area products. The resistance of the magnetic tunneljunction material, expressed as the resistance-area, has been shown tovary exponentially with both the metal layer's thickness, oxidation dosefor thickness, and dose values that produce a high magnetoresistanceratio. Thus, obtaining a thinner tunnel barrier without reducing themagnetoresistance ratio is one of the key factors to achieving a lowresistance-area product or device.

[0010] Accordingly, a need exists for an improved tunnel barrier filmwhich has lower resistance and in which the tunnel barrier height andfinal overall barrier resistance can be modified. Additional needs existfor an improved tunnel barrier film with reduced chances of pinholeformation and which can work in temperatures greater than 300° C. Anadditional needs also exist for a tunnel barrier film having reducedroughness at the tunnel-barrier interfaces and which mitigate oxidationproblems.

BRIEF SUMMARY OF THE INVENTION

[0011] The present invention provides an ALD deposited multilayerdielectric tunnel barrier film for use in magnetic tunnel junctiondevices, and a method of fabrication therefor. The tunnel barrier filmhas reduced resistance and good deposition conformality. An ALDdeposited tunnel barrier film, in accordance with the invention, isformed of alternating layers of sequence with plasma or thermaldensification steps, to create controlled resistance tunnel barrierlayers, which reduce or eliminate pinhole formation and breakdown areasin the films.

[0012] The method aspect of the invention comprises providing an oxidelayer, on a first nitride layer, and a second nitride layer on the oxideinsulation area. The first nitride layer is disposed on a semiconductorsubstrate containing a first ferromagnetic film. While the secondnitride layer interfaces with a second ferromagnetic film. By conductingthe formation of the multilayer dielectric tunnel barrier through atomiclayer deposition reactions coupled with thermal anneals, plasmaprocessing, and densification techniques; a highly improved andcontrolled multilayer tunnel barrier can be achieved which provides ahigher breakdown point, lower pinhole occurrences, and good tunnelingcharacteristics for magnetic tunnel junctions.

[0013] The enhanced multilayer tunnel barrier structure is produced byalternating layers of nitride i.e., AlN, and oxide i.e., Al_(x)O_(y),through atomic layer deposition reactions. The atomic layer depositionreactions allow precise control over the thickness of the alternatinglayers of nitride and oxide. The thickness of these alternating nitrideand oxide layers can be utilized to change the final magnetoresistanceof the barrier or barrier height, and reduce the chances of pinholeformation. Furthermore, utilizing ALD processes allows formation of thetunnel barrier structure to occur at temperatures below 300° C.,ensuring stability of the alternating layers.

[0014] Therefore, the present invention provides a multilayer dielectrictunnel barrier that has a substantially reduced overall resistance thanthat associated with conventional structures and methods, whilepermitting precise tailoring of the thicknesses of the various layers inthe tunnel barrier structure. The present invention also provides formemory devices which have reduced pinholing; improved magneticcharacteristics, by reducing the occurrence of oxidation of theferromagnetic materials on either side of the barrier; and anatomicallysmooth tunnel barrier layer interfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] These and other features and advantages of the present inventionwill become more fully apparent from the following detailed descriptionof exemplary embodiments of the invention which are provided inconnection with the accompanying drawings.

[0016]FIG. 1 is a graphical illustration of a reaction vessel used incarrying out the method aspects of the invention and prior to commencingthe different reaction sequences.

[0017]FIG. 2A is a graphical illustration of the operation of the FIG. 1reaction vessel carrying out a first processing sequence.

[0018]FIG. 2B is a graphical illustration of purging the FIG. 1 chamberafter the first processing sequence.

[0019]FIG. 2C is a graphical illustration of operating the FIG. 1reaction vessel carrying out a second processing sequence.

[0020]FIG. 2D is a graphical illustration of purging the FIG. 1 chamberafter the second processing sequence.

[0021]FIG. 2E is a cross-sectional view of the formation of a firstnitride junction layer conducted in accordance with the presentinvention through methods depicted in FIGS. 2A-2D.

[0022]FIG. 3A is a graphical illustration of the first processingsequence in forming an intermediate junction layer.

[0023]FIG. 3B is a graphical illustration of purging the FIG. 3A chamberafter the first processing sequence.

[0024]FIG. 3C is a graphical illustration of operating the FIG. 3Breaction vessel carrying out a second processing sequence.

[0025]FIG. 3D is a graphical illustration of purging the FIG. 3C chamberafter the second processing sequence.

[0026]FIG. 3E is a cross-sectional view of the formation of theintermediate junction layer, formed over the first nitride junctionlayer, conducted in accordance with the processes depicted in FIGS.3A-3D.

[0027]FIG. 4 is a cross-sectional view of the final reaction sequenceused in formation of the second nitride junction layer conducted inaccordance with the processes depicted in FIGS. 2A-2D.

[0028]FIG. 5 is a graphical illustration of plasma annealing the secondnitride junction layer formed in accordance with the processes depictedin FIGS. 2A-2D.

[0029]FIG. 6 is a cross-sectional view of a magnetic tunnel junctionbarrier film constructed in accordance with the processes depicted inFIGS. 2A-2D.

[0030]FIG. 7 is a cross-sectional view of a magnetic tunnel junctionbarrier film and the formation of the intermediate junction layerconstructed in accordance with the processes depicted in FIGS. 3A-3D.

[0031]FIG. 8 is a cross-sectional view of a magnetic tunnel junctionbarrier film and the formation of the second nitride junction layerconstructed in accordance with the processes depicted in FIGS. 2A-2D.

[0032]FIG. 9 is a cross-sectional view of a multilayer magnetic tunneljunction barrier film constructed in accordance with the presentinvention.

[0033]FIG. 10 is a cross-sectional view of a magnetic tunnel junctiondevice constructed in accordance with the present invention.

[0034]FIG. 11 is a block diagram of a system utilizing a magnetic tunneljunction device constructed in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0035] The present invention will be understood from the followingdetailed discussion of the exemplary embodiments which is presented inconnection with the accompanying drawings.

[0036] The present invention provides a multilayer dielectric tunnelbarrier used in magnetic tunnel junction devices and its method offabrication. The multilayer film has lower barrier layer resistance, isvery conformal, and can be made as a thicker or thinner film with fewerpinholes.

[0037] In the following description, specific details such as layerthicknesses, process sequences, and material compositions are set forthto provide a complete understanding of the present invention. However,it will be obvious to one skilled in the art that the present inventioncan be employed without using such specific details. In addition, inorder for a simplified description, techniques, processes, and equipmentthat are well-known in the art have not been described in detail.

[0038] For purposes of the present invention, the tunnel barrier isdefined as the dielectric portion between two ferromagnetic layers. Thecombination of alternating layers of nitride, oxide, and nitride,deposited using ALD techniques, form the tunnel barrier. The electricalbarrier height may be altered by changing the relative thicknesses ofthe nitride and oxide layers. The tunnel barrier thickness is changedsimply by the number of ALD deposition steps used in forming thealternating nitride and oxide layers.

[0039]FIG. 1 is a graphical illustration of a reaction vessel 1 whichcan be employed for magnetic tunnel junction barrier film formation. Asemiconductor wafer 2 is disposed on a temperature controlled chuck 3.Heated gas lines 9 and 10 are utilized to introduce gases into thereaction vessel 1 during fabrication of the tunnel barrier layers. Thetemperature controlled chuck 3 temperature can range from approximately25° C. to approximately 250° C. The semiconductor wafer 2 has beenpreviously processed to the point where a first ferromagnetic layer isprovided on the exposed wafer surface.

[0040] The invention provides a first nitride junction layer on thefirst ferromagnetic layer. For purposes of a simplified description, theinvention will be described below with use of AlN as comprising thefirst and second nitride junction layers. However, nitride layers suchas Si_(x)N_(y), TiN, HfN, TaN, and other alternative nitride layersknown in the art, can also be used to form the first and second nitridejunction layers. In addition, although the reactant utilized in thisinvention is described as NH₃ to form the first and second nitridejunction layers, other reactants well-known in the art such as N₂(plasma) or N from an atomic source (essentially a plasma that splits N₂into N) can be utilized with equal effectiveness. Furthermore, althoughTMA is the reactant utilized to form the first and second nitridejunction layers, other reactants well-known in the art such as DimethylAmine Alane (DMAA), Al(CH₃)₂NH₂ can be used with equal effectiveness.

[0041] To begin fabrication of a monolayer of the first nitride junctionlayer, in the first processing step, the reaction vessel 1 is firstpumped down to a pressure at least less than 0.01 Torr i.e., a vacuumenvironment. Heated gas line 9 allows an initial reactant such asAl(CH₃)₃ (TMA) 6 to enter reaction vessel 1. Heated gas line 10 allows asecond reactant to enter reaction vessel 1, such as water (H₂O) 7 orammonia (NH₃) 7. However, either heated gas line 9 or 10 may be utilizedto send the initial reactant into the reaction vessel 1.

[0042] Gas lines 9 and 10 are heated to a temperature of approximately40° C. to approximately 120° C. depending upon the reactants utilized.For instance, heated gas line 10, when carrying H₂O 7, should have atemperature at least greater than 100° C. to help avoid condensation ofthe reactant in heated gas line 10. Whereas, heated gas line 9, whencarrying TMA 6, would only need to be heated from approximately 50° C.to approximately 60° C. An additional example is if O₃ is used as areactant, the heated gas line utilized would not require a temperatureabove 50° C. In essence, the temperature of the heated gas lineutilized, just needs to be high enough to avoid condensation of thereactants in the heated gas line.

[0043] Either TMA 6, from heated gas line 9, or NH₃ 7 from heated gasline 10 can be introduced as the first reactant into reaction vessel 1.If TMA 6 is introduced as the initial reactant through heated gas line9, NH₃ 7 is then introduced as the second reactant through heated gasline 10 to form an AlN monolayer. Whereas, if NH₃ 7 is introduced as theinitial reactant through heated gas line 10, TMA 6 is then introduced asthe second reactant through heated gas line 9 to form the AlN monolayer.As described below, alternating depositions of the first reactant andsecond reactant will result in a nitride junction layer i.e., an AlNfilm, of a desired thickness. For purposes of a simplified description,the invention will be described below with use of TMA 6 as the initialreactant. However, the invention is equally effective if NH₃ 7 is usedas the initial reactant.

[0044] Referring now to FIG. 2A, after the reaction vessel 1, containingthe semiconductor wafer 2, is pumped down to a pressure at least lessthan 0.01 Torr, TMA 6 is introduced at a rate of approximately 10 sccmto approximately 50 sccm through heated gas line 9 into the reactionvessel 1. The TMA 6 is transported to the semiconductor wafer surface 2by an inert carrier gas 4 such as Ar (Argon). However, other inertcarrier gases that are non-reactive can also be utilized with equaleffectiveness. Wafer 2 is dosed with a short pulse of TMA 6 to adsorb acontinuous monolayer of TMA 6 on the wafer 2 surface. During TMA 6adsorption, the reaction vessel 1 is held at a pressure of approximately0.1 Torr to approximately 200 Torr, for a period of approximately 1second to approximately 10 seconds after deposition of Al as a monolayerfrom the TMA 6 reactant.

[0045] Referring now to FIG. 2B, a non-reactive gas 4 such as Ar, ispassed through heated gas lines 9 and 10 to purge heated gas lines 9 and10 and the reaction vessel 1 of residual reactant i.e., TMA 6. AlthoughAr is utilized as the non-reactive purge gas, any non-reactive or inertgas may be utilized as the purge gas with equal effectiveness. Thenon-reactive gas 4, is introduced into the reaction vessel 1 throughheated gas lines 9 and 10 at a rate of approximately 50 sccm. AlthoughFIG. 2B illustrates a flow of purge gas through heated gas lines 9 and10 which provides a quicker purge of the reaction vessel 1 and heatedgas lines 9 and 10, it is also possible to supply the non-reactive purgegas only through the heated gas line that supplied the initial reactant;here, in heated gas line 9, in the process step shown in FIG. 2A.Whereas if NH₃ 7 is the initial reactant, the non-reactive purge gas 4can be supplied through heated gas line 10.

[0046] After the purge depicted in FIG. 2B, FIG. 2C graphicallyillustrates that an inert carrier gas 4 such as Ar, is passed throughheated gas line 10 carrying a second reactant i.e., NH₃ 7 into reactionvessel 1. NH₃ 7 is introduced at a rate of approximately 10 sccm toapproximately 50 sccm into reaction vessel 1. The reaction vessel 1 isheld at a pressure of approximately 0.1 Torr to approximately 200 Torr,for a period of approximately 1 second to approximately 10 secondsduring introduction of the second reactant into reaction vessel 1. NH₃ 7provides nitrogen atoms which are deposited as a monolayer on the wafer2 and bonds with the Al atoms previously deposited from the firstprocessing sequence; thus, providing a monolayer of AlN on the surfaceof wafer 2.

[0047] After nitradation from the introduction of NH₃ 7, reaction vessel1 is purged again by passing a non-reactive gas 4 such as Ar, throughheated gas lines 9 and 10 in order to purge heated gas lines 9 and 10and reaction vessel 1 as shown in FIG. 2D. The non-reactive gas 4 isintroduced at a rate of approximately 50 sccm. This step removes thereaction byproduct i.e., CH₄ and residual NH₃ 7, from reaction vessel 1and heated gas lines 9 and 10. Although FIG. 2D illustrates the inertpurge gas 4 passing through both heated gas lines 9 and 10 into reactionvessel 1 for a faster purge; it is also possible to just pass the inertpurge gas 4 through the heated gas line that introduced the secondreactant. The resulting interaction between TMA 6 that was introduced inFIG. 2A and NH₃ 7 introduced in FIG. 2C, results in a monolayer ofreacted AlN which is AlNH₂ and some AlNH. AlNH₂ and AlNH can then besubsequently reduced to Al—N—Al upon reaction with another TMA 6 dose byproceeding again with the processing sequences depicted in FIGS. 2A-2B.

[0048]FIG. 2E is a cross-sectional view of the formation of the firstnitride junction layer (AlN) on a first ferromagnetic layer after onecycle of the processing sequences depicted in FIGS. 2A-2D are carriedout. TMA is not a stable compound and automatically reacts if exposed tothe atmosphere. Thus, the processes depicted in FIGS. 2A-2D, must becarried out in a vacuum-like atmosphere to prevent TMA from prematurelyreacting. TMA's volatility is an additional reason that reaction vessel1 and heated gas lines 9 and 10 must be purged prior to introducing asecond reactant in the processing sequences depicted in FIGS. 2B and 2D.

[0049] Initially, TMA is deposited on the first ferromagnetic layer(FIG. 2E(1)) provided on the wafer 2 as depicted in FIG. 2E(2). TMAremains stable and non-volatile in reaction vessel's 1 vacuum-likeenvironment and upon attachment goes to Al(CH₃)₂. Referring now to FIG.2E(3), which depicts the formation of AlNH₂; the introduction of thesecond reactant NH₃, causes the methyl groups of TMA to disassociatefrom Al. As mentioned previously, Dimethyl Amine Alane (DMAA),Al(CH₃)₂NH₂ can also be used with equal effectiveness in forming the AlNpart of the barrier. The methyl groups disassociate from TMA since thebond formation of Al—N is favorable over the Al—C bond (i.e., liberatesenergy upon formation driving the bond formation reaction). Theresulting H from NH₃ bonds to the disassociated methyl groups of TMA toform the reaction byproduct CH₄. Reaction vessel 1 and heated gas lines9 and 10 are then purged as depicted in FIG. 2D. This results inresidual unreacted NH₃ and CH₄ byproducts to be expunged from reactionvessel 1 and the wafer 2 surface leaving a monolayer of AlNH₂ and AlNHto be reacted with another TMA molecule building Al—N—Al layers forminga pristine AlN film. The surface chemical reactions in forming an AlNmonolayer are well-known in the art.

[0050] FIGS. 2A-2E respectively illustrates one continuous monolayer ofreacted AlN deposited on wafer 2 after one cycle of the processingsequences depicted in FIGS. 2A-2D has been completed. The processingsequences depicted in FIGS. 2A-2D can be repeated to form additionalmonolayers of AlN to achieve the desired thickness of the first nitridejunction layer i.e., AlN. For instance, a monolayer of AlN on thesurface will have H or H₂ such as AlNH or AlNH₂, but when reacted withanother layer of TMA the monolayer of AlN goes to Al—N—Al as describedpreviously. Thus, additional monolayers of AlN can easily be fabricatedaccording to the desired thickness.

[0051] Although the embodiment of the invention illustrated in FIGS.2A-2D introduces Al atoms first and then nitrogen atoms second informing the AlN monolayer, the process can also be modified as notedabove, to begin with a nitrogen atom layer and then an Al atom layer. Inthis case, NH₃ 7 is utilized as the initial reactant, depicted in FIG.2C, in forming the first nitride junction layer (AlN). After thenitrogen atom depositions, reaction vessel 1 is purged as depicted inFIG. 2D. Following the purge, TMA 6 is introduced, as depicted in FIG.2A, and then reaction vessel 1 is purged again as shown in FIG. 2B tocomplete one monolayer of AlN.

[0052] The processing sequences, depicted in FIGS. 2A-2D, results in ananatomically smooth monolayer of approximately 0.8 to approximately 1Angstrom (A°) of AlN deposited on the first ferromagnetic layer of wafer2. As noted, the process flow, depicted in FIGS. 2A-2D, can be repeatedany number of times as desired to fabricate additional monolayers of AlNon wafer 2 to achieve the desired thickness of the first nitridejunction layer i.e., AlN. Typically, approximately 1 to approximately 68monolayers of AlN is sufficient to protect the bottom ferromagneticelectrode and form the first nitride junction layer. This results in afirst nitride junction layer of a thickness of approximately 0.8 A° toapproximately 58 A°. The thickness of the first nitride junction layercan be tailored to provide the required magnetoresistance for any givendevice.

[0053] After its formation, the first AlN nitride junction layer canthen be thermally annealed at a temperature of approximately 200° C. toapproximately 250° C. This anneal occurs for a duration of approximatelyone minute to approximately ten minutes in a nitrogen (N₂) or oxygen(O₂) atmosphere. It is preferred that the first AlN nitride junctionlayer utilize a N₂ atmosphere in a thermal anneal to reduce the chanceof oxidation at the first ferromagnetic film layer i.e., the initialferromagnetic film provided on the semiconductor wafer. As a result ofthe thermal anneal, the level of impurities in the AlN layer isdecreased. Specifically, the thermal annealing process releases anyunreacted reactants such as TMA 6, releases the final CH₃ groups fromthe last layer of TMA 6 deposited, and drives out any trapped residualhydrogen in the film from NH₃ 7. Therefore, the process of thermallyannealing the first AlN nitride junction layer aids in completion ofnitride formation and reduces the hydrogen content of the film.

[0054] Once the first AlN nitride junction layer is formed to a desiredthickness, an intermediate junction layer i.e., an oxide layer, isprovided on wafer 2 as depicted in FIGS. 3A-3D. The intermediatejunction layer such as an oxide layer, can be comprised of Al_(x)O_(y),HfO, Ta₂O₅, SiO₂, or combinations thereof and other materials well-knownin the art. For purposes of a simplified description, the intermediatejunction layer i.e., an oxide layer, is described as an Al_(x)O_(y)layer. Either TMA 6, from heated gas line 9, or H₂O 7 from heated gasline 10 can be introduced as the first reactant into reaction vessel 1.If TMA 6 is introduced as the first reactant through heated gas line 9,H₂O 7 is then introduced as the second reactant through heated gas line10 in forming the Al_(x)O_(y) layer. Whereas, if H₂O 7 is introduced asthe first reactant through heated gas line 10, TMA 6 is then introducedas the second reactant through heated gas line 9 to form an Al_(x)O_(y)intermediate junction layer. As described below, alternating depositionsof the first reactant and second reactant will result in an intermediateoxide junction layer i.e., an oxide layer (Al_(x)O_(y)), of a desiredthickness provided on the first nitride junction layer (AlN).

[0055] For purposes of a simplified description, the invention will bedescribed below with use of TMA 6 as the initial reactant. However, theinvention is equally effective if H₂O 7 is used as the initial reactant.Furthermore, for purposes of simplification, the invention will bedescribed below with use of H₂O 7 as the second reactant in forming theAl_(x)O_(y) intermediate oxide junction layer. However, other reactantssuch as O₃, H₂0₂, and other alternative reactants well-known in the art,can also be used as the second reactant in forming the Al_(x)O_(y)intermediate oxide junction layer with equal effectiveness.

[0056] As shown in FIG. 3A, TMA 6 is introduced as the first reactantthrough heated gas line 9 into reaction vessel 1 and transported to thesemiconductor wafer 2 by an inert carrier gas 4 such as Ar. TMA 6 isintroduced at a rate of approximately 10 sccm to approximately 50 sccmas the first reactant through heated gas line 9 into reaction vessel 1.Wafer 2 is dosed with a short pulse of TMA 6 to adsorb a continuousmonolayer of Al on the wafer 2 surface. The reaction vessel 1 is held ata pressure of approximately 0.1 Torr to approximately 200 Torr, for aperiod of approximately 1 second to approximately 10 seconds during Alatom depositions.

[0057] Next, as shown in FIG. 3B, an inert gas 4 i.e., Ar, is passedthrough heated gas lines 9 and 10, to purge heated gas lines 9 and 10and reaction vessel 1 of residual TMA 6. The non-reactive gas 4 isintroduced into reaction vessel 1 through heated gas lines 9 and 10 at arate of approximately 50 sccm. Although FIG. 3B illustrates the inertpurge gas 4 passing through both heated gas lines 9 and 10 into reactionvessel 1 for a faster purge, it is also possible to just pass the inertpurge gas 4 through the heated gas line introducing the first reactant.If H₂O 7 is the initial reactant and TMA 6 is the second reactant, theinert purge gas would then be applied through heated gas line 10.

[0058] Next, as shown in FIG. 3C, an inert carrier gas 4 i.e., Ar, flowsthrough heated gas line 10 carrying H₂O 7 into reaction vessel 1. H₂O 7is introduced into reaction vessel 1 at a rate of approximately 10 sccmto approximately 50 sccm. Reaction vessel 1 is held at a pressure ofapproximately 0.1 Torr to approximately 200 Torr, for a period ofapproximately 1 second to approximately 10 seconds during theintroduction of H₂O 7. H₂O 7 provides oxygen atoms which are depositedas a monolayer on the wafer 2 and bonds with the Al atoms previouslydeposited from the first processing sequence; thus, providing acontinuous monolayer of Al_(x)O_(y) on the first nitride junction layerprovided on the wafer 2 surface.

[0059]FIG. 3D graphically illustrates the introduction of an inert gas 4i.e., Ar, through heated gas lines 9 and 10, to purge heated gas lines 9and 10 and reaction vessel 1. The non-reactive gas 4 enters reactionvessel 1 through heated gas lines 9 and 10 at a rate of approximately 50sccm. The non-reactive gas 4 serves to remove the reacted CH₄ andresidual H₂O 7. Again, as mentioned in previous paragraphs, the inertpurge gas 4 need only be supplied through heated gas line 10 if desired.

[0060]FIG. 3E is a cross-sectional view of the formation of theAl_(x)O_(y) intermediate oxide junction layer after one cycle of theprocessing sequences depicted in FIGS. 3A-3D are carried out. Theintroduction of H₂O into reaction vessel 1, produces an Al_(x)O_(y)monolayer by reacting with the TMA as depicted in FIG. 3E(4). The bondformation between the hydroxyl groups (OH) and Al is a far more stablebond (i.e., more energetically favorable) than the C and Al bond of TMA.H₂O encounters the Al—CH₃ bond and the Al—OH bond is energetically morefavorable driving the disassociation reaction of the methyl groups fromAl and OH groups from H. Thus, the Al—OH bond forms leaving CH₃ whichdisassociates and picks up the other hydrogen from the Al—OH reactionleaving CH₄ as the by-product as depicted in FIG. 3E(3). The secondpurge, as depicted in FIG. 3D, removes the reacted CH₄ and residualunreacted reactants from reaction vessel 1, leaving a continuousmonolayer of Al_(x)O_(y) (FIG. 3E(4)). The surface chemical reactionsare well-known in the art.

[0061] FIGS. 3A-3E respectively illustrates one continuous monolayer ofthe Al_(x)O_(y) layer after one processing cycle has been completed. Theprocessing sequences in FIGS. 3A-3D can be repeated to fabricateadditional monolayers to the Al_(x)O_(y) layer until a desired thicknessis achieved. Although the embodiment of the invention illustrated inFIGS. 3A-3D deposits Al first, and then OH second to form an Al_(x)O_(y)monolayer, the process can also be modified to deposit OH first ratherthan second. Thus, H₂O 7 can be utilized as the initial reactant, asdepicted in FIG. 3C, in forming the intermediate oxide junction layer(Al_(x)O_(y)). After the OH depositions, reaction vessel 1 is purged asdepicted in FIG. 3D. Following this, TMA 6 is introduced, as depicted inFIG. 3A, and then reaction vessel 1 is purged, as shown in FIG. 3B, tocomplete one monolayer of Al_(x)O_(y).

[0062] As a result, the processing sequences depicted in FIGS. 3A-3D,results in an anatomically smooth monolayer of approximately 0.8 toapproximately 1 Angstrom (A°) of Al_(x)O_(y) deposited on the firstnitride junction layer 20 of wafer 2 (FIG. 3E(1)). As noted, the processflow, depicted in FIGS. 3A-3D, can be repeated any number of times asdesired to fabricate additional monolayers of Al_(x)O_(y) provided onthe first nitride junction layer 20, to achieve the desired thickness ofthe intermediate oxide junction layer i.e., Al_(x)O_(y). Typically,approximately 1 to approximately 68 monolayers of Al_(x)O_(y) issufficient to form the intermediate oxide junction layer. As a result,the total thickness of the Al_(x)O_(y) layer is approximately 0.8 A° toapproximately 58 A°. However, the thickness of the Al_(x)O_(y) layer canbe tailored to provide the required magnetoresistance for any givendevice.

[0063] The completed Al_(x)O_(y) intermediate oxide junction layer canthen be thermally annealed at a temperature of approximately 200° C. toapproximately 250° C., for approximately one to approximately tenminutes, in a N₂ or O₂ atmosphere. Alternatively, an O₂ or N₂ plasma canbe utilized rather than a thermal anneal. It is preferred that theAl_(x)O_(y) intermediate oxide junction layer is thermally annealed in aN₂ atmosphere to reduce the chance of oxidation. The process step ofthermally annealing the Al_(x)O_(y) intermediate oxide junction layer,is to improve film density and reduce pinholing. The thermal annealreleases any unreacted reactants and drives out any trapped hydrogen;thereby, reducing the number of impurities present in the intermediateoxide junction layer. This process results in a tunnel junction barrierthat has two completed layers, the first nitride junction layer 20 andthe intermediate oxide junction layer 30 depicted in FIG. 3E(4). Thecombined thickness of these layers are approximately 1.6 A° toapproximately 59 A°.

[0064] Referring now to FIG. 4, after formation of the Al_(x)O_(y)intermediate oxide junction layer 30 to a desired thickness, a secondnitride junction layer 40 is provided on top of the Al_(x)O_(y)intermediate oxide junction layer 30. For purposes of a simplifieddescription, the invention will be described below with use of AlN asthe second nitride junction layer 40. However, similar nitride layerssuch as Si_(x)N_(y), TiN, HfN, TaN, and other alternative nitride layersknown in the art, can also be used to form the second nitride junctionlayer 40.

[0065] The second nitride junction layer 40 is an AlN nitride junctionlayer provided on the intermediate oxide junction layer 30 describedabove. The AlN second nitride junction layer 40 is formed utilizing thesame processing sequences depicted in FIGS. 2A-2D, and as described inpreceding paragraphs 42 to 55 prior to deposition of the topferromagnetic layer. The thickness of the AlN second nitride junctionlayer 40 can be tailored to any magnetoresistance that would be requiredfor any given device.

[0066] An additional embodiment of the present invention does notutilize the sequences depicted in FIGS. 2C-2D in completing formation ofthe second nitride junction layer 40. It is preferred that the secondnitride junction layer 40 react with NH₃ 7 to avoid exposure to O₂ orother materials on its way to undergoing a plasma anneal. FIGS. 2A-2Ddepict processing sequences where Al atoms 6 are first depositedfollowed by N atom depositions 7. However, the processes depicted inFIGS. 2C-2D involving N atoms depositions 7 in reaction vessel 1 can beeliminated by utilizing an alternative processing sequence.

[0067] For example, Al atoms 6 are first deposited as depicted in FIGS.2A-2B. These Al atoms 6 do not need to subsequently react with NH₃ 7 toform the second nitride junction layer, as depicted in FIGS. 2C-2D, ifan alternative processing sequence is used that ignites a N₂ plasma todensify the film such as a plasma anneal. This alternative processingstep serves to provide the necessary N atoms in forming the second AlNnitride junction monolayer when the processing steps depicted in FIGS.2C-2D are not utilized.

[0068] It is preferred that the resulting second AlN nitride junctionlayer 40, FIG. 4(d), undergo a plasma anneal to improve the overallperformance of the dielectric tunnel barrier. The plasma annealprocessing step is preferred whether FIGS. 2A-2D are utilized, or FIGS.2A-2B are utilized in forming the second nitride AlN monolayer. Theplasma anneal processing step ensures pinhole free dense tunnel barrierfilms, reduces impurities (unreacted reactants), and stabilizes thetunnel barrier film against high temperatures and humidity.

[0069]FIG. 5 graphically illustrates a plasma anneal process on thesecond AlN nitride junction layer after the desired thickness of themultilayer film has been achieved. The plasma densification process isnot used on the first two layers (the first nitride junction layer andthe intermediate oxide junction layer) of the dielectric tunnel barrierdevice in order to avoid damaging the bottom ferromagnetic layer. Thefirst nitride junction layer and intermediate oxide junction layerundergo thermal anneals and do not require the step of plasmadensification as the second nitride junction layer does.

[0070] The plasma densification process, conducted only on the secondnitride junction layer, can be carried out in the reaction vessel 1 ofFIG. 1, as depicted in FIG. 5, or in a separate chamber with an Rf,microwave plasma, or glow discharge source. The reaction vessel 1 (orseparate chamber) is backfilled with N₂ 7 and the inductively coupledplasma source 5, at the top of reaction vessel 1 is started.

[0071] FIGS. 6-9 are cross-sectional views of the different alternatinglayers of a tunnel barrier structure created by utilizing the processingsequences depicted in FIGS. 1-5. FIG. 6 is a cross-sectional view afterthe first nitride junction layer 20 i.e., AlN, is formed over the bottomferromagnetic layer 10 and thermally annealed. FIG. 6 depicts that thefirst nitride junction layer's 20 thickness can range from approximately0.8 A° to approximately 58 A°. FIG. 7 is a cross-sectional view afterthe intermediate oxide junction layer 30 i.e., Al_(x)O_(y), is formedover the first nitride junction layer 20 and thermally annealed. FIG. 7depicts that the intermediate oxide junction layer 30 can range fromapproximately 0.8 A° to approximately 58 A° in thickness. FIG. 7 alsodepicts that the combined thickness of the intermediate oxide junctionlayer 30 and the first nitride junction layer is approximately 1.6 A° toapproximately 59 A°.

[0072]FIG. 8 is a cross-sectional view after the second nitride junctionlayer 40 i.e., AlN, which is provided on the intermediate oxide junctionlayer 30, after undergoing a nitrogen plasma anneal process. FIG. 8depicts that the second nitride junction layer 40 can range fromapproximately 0.8 A° to approximately 58 A° in thickness. FIG. 9 is across-sectional view of a magnetic tunnel barrier device, constructedutilizing the methods of the present invention. As shown, a pair offerromagnetic layers 10 and 50, are separated by a multilayer tunneljunction barrier (20, 30, 40) constructed as described above. FIG. 9depicts that the completed multilayer tunnel junction barrier (20, 30,40) can range from approximately 2.4 A° to approximately 60 A° in totalthickness.

[0073]FIG. 10 is a cross-sectional view of a magnetic tunnel junctionmemory element suitable for use in an MRAM memory device utilizing themultilayer dielectric tunnel barrier (20, 30, 40) constructed inaccordance with the present invention. The multilayer tunnel barrier(20, 30, 40) interfaces with two ferromagnetic film layers (10 and 50),one of which is pinned and the other of which is free. Althoughalternating individual nitride-oxide-nitride layers (20, 30, 40) eachhave a thickness of approximately 0.8 A° to approximately 58 A°, theoverall thickness of the multilayer tunnel barrier (20, 30, 40)constructed in accordance with the present invention, does not exceedapproximately 60 A°. Whereas, the multilayer tunnel barrier (20, 30, 40)can be as thin as approximately 2.4 A° thick. The top and bottomferromagnetic layers (10 and 50) may also interface with a capping 60and seeding layer 0 respectively, depending on the device that willutilize the multilayer tunnel barrier (20, 30, 40).

[0074]FIG. 11 is a block diagram of a processor system utilizing themultilayer dielectric tunnel barrier structure as described above. Theprocessor system 500 may be a computer system comprising CPU 510 whichexchanges data with an MRAM memory element 540 containing memory cellsconstructed as described above. The MRAM memory element 540 communicateswith CPU 510 over one or more buses and/or bridges 570 directly orthrough a memory controller. The buses and/or bridges 570 also allow theCPU 510 to internally communicate with I/O devices 520, 530, read-onlymemory (ROM) devices 540, and peripheral devices such as a floppy diskdrive 550 and a compact disk CD-ROM drive 560, as is well known in theart.

[0075] The present invention also provides a magnetic memory device suchas a storage cell which can be fabricated with a multilayer tunnelbarrier that is comprised of only two monolayers of AlN and onemonolayer of Al_(x)O_(y), with a combined overall thickness ofapproximately 2.4 A° to approximately 3 A°.

[0076] The multilayer tunnel barrier fabricated utilizing the methodsdescribed above, has reduced pinholes, improves signal levels, improvesoverall device speed, and provides anatomically smooth surfaces. As aresult, any combination of the thicknesses of the respective alternatinglayers of nitride i.e., AlN, and oxide i.e., Al_(x)O_(y), can be useddepending upon the device that will utilize the present invention. Theonly limiting factor is that the resulting tunnel barrier structurepossess a minimum thickness of approximately 2.4 A° and a maximumthickness of approximately 60 A°.

[0077] The present invention is equally effective with alternatinglayers of nitride-oxide-nitride that are equal in thickness to eachother. As a result, the tunnel barrier can be tuned (i.e., themagnetoresistance) by choosing the thicknesses of each alternating layerwithin a nitride or oxide layer or the nitride or oxide layer itself.Examples of using the present invention include creation of a tunnelbarrier that has a 4 A° AlN layer (a first nitride junction layer), 4 A°Al_(x)O_(y) layer (an intermediate oxide junction layer), and a 2 A° AlNlayer (a second nitride junction layer). Other possibilities include atunnel barrier having different layers of thickness such as: 6 A° AlN,10 A° Al_(x)O_(y), and 6 A° AlN; a 20 A° AlN, 5 A° Al_(x)O_(y), and 30A° AlN; 4 A° AlN, 4 A° Al_(x)O_(y), and 4 A° AlN; 2 A° AlN, 6 A°Al_(x)O_(y), and 2 A° AlN; 4 A° AlN, 10 A° Al_(x)O_(y), and 4 A° AlN;and 20 A° AlN, 40 A° Al_(x)O_(y), and 20 A° AlN for instance.

[0078] As a result, a multitude of combinations can result by utilizingthe present invention and methods described above depending upon thedevice that the tunnel barrier is being created for i.e., themagnetoresistance desired. For instance, if one wanted to make atunneling curve very lopsided from negative potential to positivepotential, one could use different thicknesses of AlN (the first andsecond nitride junction layers) which would change the tunnelingcharacteristics depending on the direction of tunneling through thedevice. If electrons pass from bottom to top rather than top to bottom,the electrons will encounter a very different tunnel barrier shape. Inaddition, to increase the total resistance of the device utilizing thepresent invention, the intermediate oxide junction layer i.e.,Al_(x)O_(y) layer, can be made thicker. Thus, the present inventionallows one to tune the resistance of any given magnetic device utilizingthe multilayer tunnel barrier as described above.

[0079] The present invention also provides a method and structurecapable of simultaneously reducing the overall resistance of the tunnelbarrier, and the occurrence of pinhole formation, while permitting filmsof various thickness to be formed. The dielectric tunnel barriersconformality and surface smoothness, is substantially enhanced comparedto those dielectric tunnel barriers associated with conventionalstructures and methods. The ALD process leaves the interfaces of thetunnel barrier structure as pristine as possible by avoiding metalmixing and overoxidation from a plasma source. Furthermore, the ALDdeposition techniques allows a multilayer tunnel barrier to be very thinimproving signal levels and overall device speeds.

[0080] The present invention also provides more precise stoichiometriccontrol over the two nitride and oxide films and barrier height.Although the invention has been described and illustrated as beingsuitable for use in a memory application, an application for example, asin an MRAM device; the invention is not limited to MRAM applications.Rather, the invention and methods described in previous paragraphs,could be employed in any processor system in which an enhanced tunnelingcharacteristic of a magnetic tunnel junction is desired.

[0081] Accordingly, the above description and accompanying drawings areonly illustrative of exemplary embodiments that can achieve the featuresand advantages of the present invention. It is not intended that theinvention be limited to the embodiments shown and described in detailherein. The invention is limited only by the scope of the followingclaims.

What is claimed as new and desired to be protected by Letters Patent ofthe United States is:
 1. A multilayer dielectric tunnel barrierstructure for use in semiconductor memory devices, said tunnel barrierstructure comprising: a substrate supporting a magnetic layer; an ALDdeposited first nitride junction layer formed over said magnetic layer;an ALD deposited intermediate junction layer formed over said firstnitride junction layer; and an ALD deposited second nitride junctionlayer formed over said intermediate tunnel junction layer.
 2. Astructure as in claim 1, wherein said magnetic layer is a ferromagneticlayer.
 3. A structure as in claim 2, wherein said ferromagnetic layer ispinned.
 4. A structure as in claim 2, wherein said ferromagnetic layeris free.
 5. A structure as in claim 1, wherein said first nitridejunction layer is formed of one or more nitride monolayers.
 6. Astructure as in claim 5, wherein said first nitride junction layer isformed of AlN.
 7. A structure as in claim 6, wherein said first nitridejunction layer has a thickness of approximately 0.8 A° to approximately58 A°.
 8. A structure as in claim 1, wherein said intermediate junctionlayer is an oxide layer.
 9. A structure as in claim 8, wherein saidoxide layer is formed of one or more monolayers.
 10. A structure as inclaim 9, wherein said oxide layer is formed of Al_(x)O_(y), HfO, Ta₂O₅,SiO₂, or combinations thereof.
 11. A structure as in claim 1, whereinsaid intermediate junction layer is formed on said first nitridejunction layer
 12. A structure as in claim 11, wherein said intermediatejunction layer and first nitride junction layer is approximately 1.6 A°to approximately 59 A° thick.
 13. A structure as in claim 12, whereinsaid intermediate junction layer has a thickness of approximately 0.8 A°to approximately 58 A°.
 14. A structure as in claim 1, wherein saidsecond nitride junction layer is formed from one or more nitridemonolayers.
 15. A structure as in claim 14, wherein said second nitridejunction layer is formed of AlN.
 16. A structure as in claim 1, whereinsaid second nitride junction layer and intermediate junction layer andfirst nitride junction layer is approximately 2.4 A° to approximately 60A° thick.
 17. A structure as in claim 16, wherein said second nitridejunction layer has a thickness of approximately 0.8 A° to approximately58 A°.
 18. A structure as in claim 16, wherein said second nitridejunction layer interfaces with a ferromagnetic layer.
 19. A structure asin claim 18, wherein said ferromagnetic layer is pinned.
 20. A structureas in claim 18, wherein said ferromagnetic layer is free.
 21. Astructure as in claim 1, wherein said first and second nitride junctionlayers are approximately 4 A° thick and the intermediate junction layeris approximately 4 A° thick.
 22. A structure as in claim 1, wherein saidfirst and second nitride junction layers are approximately 2 A° thickand the intermediate junction layer is approximately 6 A° thick.
 23. Astructure as in claim 1, wherein said first and second nitride junctionlayers are approximately 4 A° thick and the intermediate junction layeris approximately 10 A° thick.
 24. A structure as in claim 1, whereinsaid first and second nitride junction layers are approximately 20 A°thick and the intermediate junction layer is approximately 40 A° thick.25. A method of fabricating a multilayer dielectric tunnel barrierstructure for use in semiconductor memory devices, said methodcomprising: providing a substrate supporting a magnetic layer; formingan ALD deposited first nitride junction layer over said magnetic layer;forming an ALD deposited intermediate junction layer over said firstnitride junction layer; and forming an ALD deposited second nitridejunction layer over said intermediate tunnel junction layer.
 26. Themethod as in claim 25, wherein said magnetic layer is a ferromagneticlayer.
 27. The method as in claim 26, wherein said ferromagnetic layeris pinned.
 28. The method as in claim 26, wherein said ferromagneticlayer is free.
 29. The method as in claim 25, wherein said first nitridejunction layer is formed of one or more nitride monolayers.
 30. Themethod as in claim 29, wherein said first nitride junction layer isformed of AlN.
 31. The method as in claim 30, wherein said first nitridejunction layer is formed in a reaction vessel with heated gas lines. 32.The method as in claim 31, wherein said gas lines are heated from atemperature of approximately 40° C. to approximately 120° C.
 33. Themethod as in claim 31, wherein said heated gas lines introduce a firstreactant into the reaction vessel.
 34. The method as in claim 33,wherein said first reactant is TMA.
 35. The method as in claim 33,wherein said first reactant is NH₃.
 36. The method as in claim 33,wherein said first reactant is purged.
 37. The method as in claim 36,wherein a second reactant is carried through a heated gas line into thereaction vessel.
 38. The method as is claim 37, wherein said secondreactant is TMA.
 39. The method as in claim 37, wherein said secondreactant is NH₃.
 40. The method as in claim 37, wherein said secondreactant is purged.
 41. The method as in claim 40, wherein said one ormore first nitride junction layers of AlN are formed.
 42. The method asin claim 41, wherein said first nitride junction layer is approximately0.8 A° to approximately 58 A° thick.
 43. The method as in claim 42,wherein said first nitride junction layer is thermally annealed.
 44. Themethod as in claim 42, wherein said first nitride junction layer is notthermally annealed.
 45. The method as in claim 25, wherein saidintermediate junction layer is an oxide layer.
 46. The method as inclaim 45, wherein said oxide layer is formed of one or more oxidemonolayers.
 47. The method as in claim 46, wherein said oxide layer isformed of Al_(x)O_(y), HfO, Ta₂O₅, SiO₂, or combinations thereof. 48.The method as in claim 47, wherein said oxide layer is formed in areaction vessel with heated gas lines.
 49. The method as in claim 48,wherein said gas lines are heated from a temperature of approximately40° C. to approximately 120° C.
 50. The method as in claim 48, whereinsaid heated gas lines introduce a first reactant into the reactionvessel.
 51. The method as in claim 50, wherein said first reactant isTMA.
 52. The method as in claim 50, wherein said first reactant is H₂O.53. The method as in claim 50, wherein said first reactant is purged.54. The method as in claim 53, wherein a second reactant is carriedthrough a heated gas line into the reaction vessel.
 55. The method as isclaim 54, wherein said second reactant is TMA.
 56. The method as inclaim 54, wherein said second reactant is H₂O.
 57. The method as inclaim 54, wherein said second reactant is purged.
 58. The method as inclaim 57, wherein said one or more intermediate junction layers ofAl_(x)O_(y) is formed.
 59. The method as in claim 58, wherein saidintermediate junction layer is formed on said first nitride junctionlayer
 60. The method as in claim 59, wherein said intermediate junctionlayer and first nitride junction layer is approximately 1.6 A° toapproximately 59 A° thick.
 61. The method as in claim 60, wherein saidintermediate junction layer has a thickness of approximately 0.8 A° toapproximately 58 A°.
 62. The method as in claim 61, wherein saidintermediate junction layer is thermally annealed.
 63. The method as inclaim 61, wherein said intermediate junction layer is not thermallyannealed.
 64. The method as in claim 25, wherein said second nitridejunction layer is formed of one or more nitride monolayers.
 65. Themethod as in claim 64, wherein said second nitride junction layer isformed of AlN.
 66. The method as in claim 65, wherein said secondnitride junction layer is formed in a reaction vessel with heated gaslines.
 67. The method as in claim 66, wherein said gas lines are heatedfrom a temperature of approximately 40° C. to approximately 120° C. 68.The method as in claim 66, wherein said heated gas lines introduce afirst reactant into the reaction vessel.
 69. The method as in claim 68,wherein said first reactant is TMA.
 70. The method as in claim 68,wherein said first reactant is NH₃.
 71. The method as in claim 68,wherein said first reactant is purged.
 72. The method as in claim 71,wherein a second reactant is carried through a heated gas line into thereaction vessel.
 73. The method as is claim 72, wherein said secondreactant is TMA.
 74. The method as in claim 72, wherein said secondreactant is NH₃.
 75. The method as in claim 72, wherein said secondreactant is purged.
 76. The method as in claim 75, wherein said one ormore second nitride junction layers of AlN is formed.
 77. The method asin claim 25, wherein said second nitride junction layer and intermediatejunction layer and first nitride junction layer is approximately 2.4 A°to approximately 60 A° thick.
 78. The method as in claim 77, whereinsaid second nitride junction layer has a thickness of approximately 0.8A° to approximately 58 A°.
 79. The method as in claim 78, wherein saidsecond nitride junction layer undergoes a nitrogen plasma anneal. 80.The method as in claim 78, wherein said second nitride junction layerdoes not undergo a nitrogen plasma anneal.
 81. The method as in claim78, wherein said second nitride junction layer interfaces with aferromagnetic layer.
 82. The method as in claim 81, wherein saidferromagnetic layer is pinned.
 83. The method as in claim 81, whereinsaid ferromagnetic layer is free.
 84. A system comprising: a processor;and a memory device coupled to said processor, at least one of saidprocessor and said memory device using a magnetic tunnel junctionstructure; at least one of said processor and said memory device andsaid magnetic tunnel junction structure comprising a multilayerdielectric tunnel barrier structure, said tunnel barrier structurecomprising: a substrate supporting a magnetic layer; an ALD depositedfirst nitride junction layer formed over said magnetic layer; an ALDdeposited intermediate junction layer formed over said first nitridejunction layer; and an ALD deposited second nitride junction layerformed over said intermediate tunnel junction layer.
 85. A system as inclaim 84, wherein said magnetic layer is a ferromagnetic layer.
 86. Asystem as in claim 85, wherein said ferromagnetic layer is pinned.
 87. Asystem as in claim 85, wherein said ferromagnetic layer is free.
 88. Asystem as in claim 84, wherein said first nitride junction layer isformed of one or more nitride monolayers.
 89. A system as in claim 88,wherein said first nitride junction layer is formed of AlN.
 90. A systemas in claim 89, wherein said first nitride junction layer has athickness of approximately 0.8 A° to approximately 58 A°.
 91. A systemas in claim 84, wherein said intermediate junction layer is an oxidelayer.
 92. A system as in claim 91, wherein said oxide layer is formedof one or more oxide monolayers.
 93. A system as in claim 92, whereinsaid oxide layer is formed of Al_(x)O_(y), HfO, Ta₂O₅, SiO₂, orcombinations thereof.
 94. A system as in claim 91, wherein saidintermediate junction layer is formed on said first nitride junctionlayer
 95. A system as in claim 94, wherein said intermediate junctionlayer and first nitride junction layer is approximately 1.6 A° toapproximately 59 A° thick.
 96. A system as in claim 95, wherein saidintermediate junction layer has a thickness of approximately 0.8 A° toapproximately 58 A°.
 97. A system as in claim 84, wherein said secondnitride junction layer is formed of one or more nitride monolayers. 98.A system as in claim 97, wherein said second nitride junction layer isformed of AlN.
 99. A system as in claim 84, wherein said second nitridejunction layer and intermediate junction layer and first nitridejunction layer is approximately 2.4 A° to approximately 60 A° thick.100. A system as in claim 99, wherein said second nitride junction layerhas a thickness of approximately 0.8 A° to approximately 58 A°.
 101. Asystem as in claim 100, wherein said second nitride junction layerinterfaces with a ferromagnetic layer.
 102. A system as in claim 101,wherein said ferromagnetic layer is pinned.
 103. A system as in claim101, wherein said ferromagnetic layer is free.